1. Field of the Invention
The present invention relates to a sheet processing apparatus equipped with a sheet processing unit which performs sheet processing, including folding, cutting, and binding, on sheets and to a sheet processing method, as well as a controlling apparatus.
2. Description of the Related Art
Recent printing systems and the like intended for the POD (print-on-demand) market are configured by connecting a printer directly with various sheet processing apparatuses (by in-line connection) and adapted to perform folding, cutting, and binding such as stapling or case binding on the printed sheets.
If such printing systems and the like perform folding and cutting in combination, a portion around a fold line produced by the folding could be cut off. Furthermore, when the folding and the binding are performed in combination, the portion around the fold line produced by the folding could be bound by staples or the like.
Therefore, in the printing systems and the like, operations on a control panel are limited so as to disable the cutting after the folding. Also, operations on the control panel are limited so as to disable the combined use of a specific folding (e.g., Z-folding) and a specific cutting (e.g., edge cutting).
Thus, in relation to the conventional printing systems and the like, a technique has been proposed in order to prevent the fold lines from being cut off. The technique involves, for example, placing two fold lines on the inner side of the respective sheet edges during Z-folding to thereby displace the fold lines so as to avoid portions around the fold lines from being cut off. Also, in relation to conventional sheet processing apparatus and the like, a technique has been proposed of determining whether or not sheets include any part to be eventually cut off and changing fold line positions based on the determination result (see Japanese Laid-Open Patent Publication (Kokai) No. 2001-163514, for example).
Also, with the conventional sheet processing apparatus and the like, if a cutting position of a sheet is affected by folding, printing of the sheet to be folded is interrupted. For the conventional sheet processing apparatus and the like, a technique has been proposed of changing fold line positions by prompting a user to enter an input for folding position adjustment again (see Japanese Laid-Open Patent Publication (Kokai) No. 2010-002859, for example).
Furthermore, some conventional sheet processing apparatuses and the like are designed to be able to extract and subsequently cut only sheets to be not subjected to folding. In relation to these conventional sheet processing apparatuses and the like, when there is a mixture of sheets which require folding and sheets which require no folding, it is proposed to sort the sheets into a type of sheet requiring folding and a type of sheet requiring no folding and then output the two types of sheet separately (see Japanese Laid-Open Patent Publication (Kokai) No. 10-186959, for example).
In relation to some conventional sheet processing apparatuses and the like, a folding position adjustment technique for a plurality of folding manners including Z-folding has been proposed (see Japanese Laid-Open Patent Publication (Kokai) No. 2006-193288, for example).
However, the use of the conventional techniques described above involve problems described below.
For example, when a specific folding such as Z-folding and a specific cutting such as edge cutting are combined, it is conceivable to use measures described in Japanese Laid-Open Patent Publication (Kokai) No. 2001-163514 and Japanese Laid-Open Patent Publication (Kokai) No. 2010-002859. In so doing, if the first folding position from a base end of the sheet is adjusted automatically, only a single folding position can be adjusted automatically. Consequently, when these measures are used, a distance between the first folding position and the second folding position from the base end of the sheet becomes fixed. This results in a Z-fold of undesirable style in which the distance of the second folding position from the base end of the sheet is longer than half the sheet.
If binding is done in addition to folding and edge cutting, only the first folding position from the base end of the sheet can be adjusted automatically as is the case with the techniques described in Japanese Laid-Open Patent Publication (Kokai) No. 2001-163514 and Japanese Laid-Open Patent Publication (Kokai) No. 2010-002859. Consequently, if the sheet marked for folding is wide, requiring a large cut width, the second folding position from the base end of the sheet will overlap the binding position, resulting in an unexpected output.